Use Of Speciation Research Articles

Isolation and purification of arsenolipids from natural marine sources for use in speciation and toxicological studies

Environmental context Arsenic exists in different chemical forms in our environment, among others as arsenolipids that are predominately found in appreciable quantities in various marine organisms (seafood). Their origin, biosynthetic pathway, toxicity and their potential biological role are not fully understood. We report purification strategies for environmental and human health relevant arsenolipids to broaden and support innovative arsenolipid research.Rational This study aims to isolate and purify common arsenolipids found in various seafood from commercially available marine sources to provide an alternative approach to the challenging chemical synthesis.Methodology Arsenic containing fatty acids and arsenic containing hydrocarbons were purified from salmon oil, and the edible dried seaweed Wakame was used for the purification of di-acyl arsenosugar phospholipids and arsenic containing hydrocarbons. The developed purification protocols apply and combine straightforward analytical techniques by means of chemical hydrolysis, solid–liquid extraction, solvent-partitioning, solid-phase extraction and preparative liquid chromatography. Elemental mass spectrometry and HPLC/mass spectrometry were used for the development of the purification protocols and the characterisation of purified natural extracts of arsenolipids.Results The salmon oil (20.0 kg) and Wakame (0.50 kg) samples contained 12.8 and 3.19 mg of lipid-soluble arsenic, respectively. The final purified extracts of arsenic fatty acids and arsenic hydrocarbons obtained from salmon oil contained 0.52 mg As in 85 mg of total mass and 2.19 mg As in 28 mg of total mass, respectively. Purification of di-acyl arsenosugar phospholipids and arsenic containing hydrocarbons from Wakame returned extracts containing 0.345 and 0.237 mg As in ≤20 mg of total mass, respectively.Discussion In a natural product approach, arsenic containing fatty acids, arsenic containing hydrocarbons and di-acyl arsenosugar phospholipids have been purified in a multi-stage process from fish oil and algae samples. In the final purified extracts, around 90% or more of the arsenic was present as mixtures of arsenolipids of their respective arsenolipid classes in only minute amounts of total mass. Application of the purified mixtures in toxicological and speciation studies will benefit the future investigation of arsenolipids.

Applying genetic algorithms with speciation for optimization of grid template pattern detection in financial markets

This paper presents a new computational finance approach. It combines a grid pattern recognition technique allied to an evolutionary computation optimization kernel based on Genetic Algorithms, creating a dynamic way to attribute a score to the signal that takes volatility into consideration and normalizing the pattern detection by fixing the grid size with the ultimate goal of reduce risk and increase profits. For pattern matching, a template based approach using a fixed size grid of weights is adopted to describe the desired trading patterns, taking not only the closing price into consideration, but also the variation of price in each considered time interval of the time series. The scores assigned to the grid of weights will be optimized by the Genetic Algorithm and, at the same time, the genetic diversity of possible solutions will be preserved using a speciation technique, giving time for individuals to be optimized within their own niche. The adoption of this approach has the goal of reducing the investment risk and check if it outperforms similar approaches. This system was tested against state-of-the-art solutions, namely the existing adaptable grid of weights and a non speciated approach, considering real data from the stock market. The developed approach using the grid of weights had 21.3% of average return over the testing period against 10.9% of the existing approach and the use of speciation improved some of the training results as genetic diversity was taken into consideration.

Thermochemistry of the Fe, Ni and Co-NH3-H2O systems as they relate to the Caron process: a review

Passivation of Fe-Ni-Co alloys during the Caron leach process is thought to result in low cobalt recoveries in ammoniacal ammonium carbonate solutions. A brief review of the available thermochemical data for the (Fe, Ni, Co)-NH3-H2O systems has been undertaken. The stability of the Co(II) and Co(III), Ni(II) and Fe(II) ammines was examined through the use of speciation and Pourbaix diagrams at 298 and 333 K and at 6 M total ammonia. Increasing the temperature reduces the stability fields of the ammines and generally constrains the thermodynamic window for the leach. The Fe(II) ammines are only thermodynamically stable under reducing conditions. Polarization experiments show that these ammines are unlikely to form if oxygen is present. Fe-Ni-Co alloy passivation may be alleviated by careful management of potential.

Use of speciation and complexation models to estimate heavy metal sorption in soils

The development of speciation and surface complexation models to calculate partitioning of metals between the soil solid phase and soil solution has made a large progress. We evaluated the use and practical applicability of an assemblage of complexation models to predict sorption of Cd, Cu, Ni, Pb and Zn. We used 353 samples which cover a wide range of soil properties and metal contents. For sorption of cations to solid and dissolved organic matter the NICA-Donnan model was used, to clay minerals a non-specific Donnan type exchange model, and to metal(hydr)oxides a two-site DDL model. Calculated solution concentrations agree well with measurements, except for Pb where calculations overestimate concentrations by one order of magnitude on average. Some highly Zn contaminated samples show relatively large deviations between measured and calculated concentrations. This is most likely caused by Zn containing minerals which are included in the total amount of reactive metals in the soil as determined by acid extraction. Hence, such models can be used for practical applications if one is aware of the possible complications. When the “total reactive metal content” includes a substantial amount of precipitated metals, which may occur for heavily contaminated soils, the model tends to overestimate concentrations in solution.

Brain abscess due to Streptococcus acidominimus: first case report

Background Streptococcus acidominimus resembles Streptococcus viridans, but they can now be differentiated by phenotypic studies. Only a single previous case of pneumonia, pericarditis, and meningitis has been reported. Case Description We recently encountered a patient with brain abscess from which S acidominimus was isolated after initially being recorded as S viridans. Because 49% of all S viridans isolated from abscesses are resistant to β-lactam antimicrobials, speciation is important as well as in vitro sensitivity testing. Streptococcus acidominimus is ordinarily sensitive to β-lactams, and the use of ceftriaxone for 6 weeks successfully resulted in cure of the brain abscess. Conclusion The use of speciation in treatment of S viridans should improve clinical outcomes.

Solvent Extraction in Hydrometallurgy: Present and Future

During the past 10 years, there have been incremental advances in the application of solvent extraction to process hydrometallurgy. The most cited areas in the literature include chemistry, chemical engineering, pilot plants, and plant operation. Within these areas, there were considerable interest in synergism, diluents, degradation, contactors, surfactants, hydrometallurgical applications, environmental and secondary applications, and health and safety. The summary to the present is followed by a prediction for the future in the above areas of interest. These include the use of speciation; improved understanding of the role of surfactants on the system; optimization through modelling, pilot plants, and contactor selection; improvements in plant operation; further new applications; and plant safety. The review has indicated that considerable knowledge is now available to optimize and improve on process design and plant applications.

The use of speciation and X-ray techniques for determining pretreatment steps for desalination

A major cost factor in the construction of desalination plants is the feed water pretreatment section. Pretreatment is necessary to prevent fouling of membranes (in electrodialysis or reverse osmosis) or heat exchange surfaces (evaporation). Various laboratory techniques are described which enable small-scale tests to be undertaken in order to determine acceptable pretreatment sequences and feasible water recoveries. A variety of effluents were subjected to evaporation or small scale reverse osmosis tests. Precipitates produced were identified by X-ray techniques. In some cases, the identification of the precipitate was, in itself, sufficient to indicate the cause of fouling, in another, identification enabled various pretreatment sequences to be modelled using chemical equilibrium computer programmes. A combination of conventional chemical analysis, X-ray techniques and computer modelling has proved successful in determining acceptable pretreatment sequences.

Rapid speciation of Haemophilus with the porphyrin production test versus the satellite test for X

The detection of porphyrins produced from omega-aminolevulinic acid was evaluated for use in speciation of the Haemophilus. Two hundred and forty-eight clinical isolates of nonhemolytic Haemophilus were tested concurrently for porphyrin production and for X and V requirements. The porphyrin production test was more rapid (4 h) and more accurate than the satellite test.